The present invention relates to a clamping device for individual tools having a pulling member arranged within a spindle whereby a tool or tool holder is clamped and centered at the spindle with the aid of the pulling member.
A plurality of clamping devices is known with which individual tools may be connected directly or via a tool holder to the spindle of a working machine. For example, German Patent 31 08 439 discloses a drilling tool with a head portion having a cylindrical fitting lug that engages a corresponding fitting bore of a tool holder. Such clamping devices are commercially available as so-called ABS clamping systems manufactured by the German company Komet. In such systems, two fastening screws are provided in the wall of the fitting bore and are diametrically opposed to one another. Their inner end faces have conical depressions which are engaged by conically shaped ends of a connecting bolt which is supported in a transverse bore of the fitting lug. The axes of the conically shaped ends of the connecting bolt and of the conical depressions of the fastening screws are staggered relative to one another. With this arrangement, by screwing the fastening screws into the fitting bore, the connecting bolt and thus the head portion is axially clamped relative to the tool holder.
Due to the cylindrical embodiment of the fitting lug the fitting lug and the corresponding fitting bore must be very precisely machined. In order to achieve clamping an exact arrangement of the fastening screws and of the connecting bolt must be ensured in order to accomplish the axial staggering which is necessary for the axial clamping. The changing operation and the clamping step are thus very time consuming and difficult.
Another clamping device for individual tools is known from German Offenlegungschrift 35 14 829 in which the spindle has a conical bore into which a conical shaft of the tool is inserted. Within the spindle radially slidable wedge elements are provided which cooperate with wedge-shaped grooves in the spindle and are connected via a cam arrangement to an axially movable pulling rod extending axially within the spindle. This clamping device requires a great constructive expenditure. Since the conical shaft of the tool must be inserted axially into the receiving bore of the spindle the exchange operation is again rather time consuming. In order for the radially movable wedge elements to generate the axial clamping, the wedge elements the wedge grooves must be provided with respective slanted surfaces within the spindle which require an exact machining and an exact mounting of the wedge elements.
With the clamping device according to European Patent 0 275 441 fastening screws are again used which cooperate via spherical intermediate elements with ends of a connecting bolt inserted in a transverse bore of the tool holder. The spherical connecting elements have clamping surfaces arranged at a slant relative to the axis of the tool, the clamping surfaces cooperating with respective slanted surfaces of the connecting bolt during the axial clamping. The connecting bolt is again supported within a cylindrical fitting piece that is inserted into a respective cylindrical fitting bore of the spindle. This clamping device also requires a great constructive expenditure and is comprised of parts which require minimal tolerances. A simple and fast tool exchange is thus impossible.
German Offenlegungschrift 38 07 140 shows a clamping device in which clamping jaws are supported at the spindle, the clamping jaws moved via a pulling rod into the release or clamping position. The tool holder engages with a cylindrical fitting sleeve the receiving bore of the spindle. The inside of the fitting sleeve is provided with groove-shaped recesses which are engaged by the clamping jaws and thus generate an axial clamping force between the spindle and the tool holder. In order to allow for a pivoting movement of the clamping jaws, an additional conical pushing part is required at the spindle. This clamping device is thus comprised of a plurality of parts. Due to the cylindrical fitting sleeve of the tool holder a very precise manufacturing of the fitting sleeve and the receiving bore of the spindle is necessary. The exchange process is difficult because the fitting sleeve of the tool holder must be exactly inserted into the receiving bore of the spindle. Because of the fitting sleeve, as described above for the other clamping device a greater insertion play must be provided in order to be able to insert the fitting sleeve with ease into the receiving bore of the spindle.
The European Patent 0 295 315 shows a clamping device in which in the side walls of the cylindrical receiving bore of the spindle radially extending fastening screws are provided which engage with conically shaped screw heads conically shaped depressions within the ends of a clamping element arranged transverse to the axis of the spindle. By fastening the fastening screws the tool holder is axially clamped at the spindle via the conical surfaces. This clamping device also requires a great constructive expenditure and is furthermore comprised of a great number of individual parts. Also, due to the insertion step the exchange process is rather time-consuming.
In the clamping device according to German Patent 38 14 550 the tool holder is provided with a conical or cylindrical centering projection via which the tool holder engages a respective receiving bore of the spindle. The spindle is provided with a centrally arranged axially extending pulling rod for moving clamping jaws radially outwardly in a translatory movement. The tool holder is axially pulled via the centering projection against the spindle. In order to generate the translatory movement of the individual clamping, jaws a complicated design of the clamping jaws, the pull rod, and the receiving bore of the spindle is necessary. Also, with the described clamping device a plurality of parts is required. Since the tool holder must be inserted with its centering projection into the receiving bore of the spindle, the exchange process requires a substantial amount of time.
German Offenlegungschrift 38 31 666 discloses a clamping device in which a projection of the tool holder is inserted into the receiving bore of the spindle. The spindle comprises a pull rod and a clamping rod arranged axially slidable therein with which the tool holder may be axially clamped at the spindle. Additionally, clamping elements are provided with which the projection of the tool holder, which extends axially into the receiving bore of the spindle, is engaged. This known clamping device is again comprised of a plurality of parts and is therefore expensive to manufacture and requires a relatively long changing time.
Another known clamping device is disclosed in German Offenlegungschrift 38 34 192 and comprises again a plurality of clamping elements disposed within the spindle. Via an axially movable actuating rod the clamping elements engage and clamp a projection of the tool holder extending into the receiving bore of this spindle. The wall of the receiving bore of the spindle as well as the outer mantle surface of the projection of the tool holder are provided with cylindrical fitting surfaces arranged axially one after another. Due to these cylindrical fitting surfaces the projection of the tool holder and the receiving bore of the spindle have a complicated design which is expensive and time-consuming to manufacture. The individual cylindrical surfaces must furthermore be produced with very small tolerances. Since the tool holder with its projection must be inserted into the receiving bore of the spindle short exchange times are not achievable.
In a further known clamping device (German Offenlegungschrift 39 04 259) the tool holder is inserted with a projection into a receiving bore of the spindle and is fastened therein with clamping jaws. The clamping jaws are permanently prestressed by an axially acting spring arrangement in the form of a cup spring package so that the jaw segments of the clamping jaws are forced radially inwardly. With a radial adjustment screw the clamping jaws are radially outwardly pivoted against the force of the spring arrangement in order to fasten the projection of the tool holder. Due to the clamping jaws and the spring arrangement a plurality of parts is required for the clamping device. Since the tool holder with its projection must be axially inserted into the receiving bore of the spindle short changing times are not achievable.
Another clamping device is known from German Offenlegungschrift 39 39 227 in which a cylindrical clamping sleeve of the tool holder extends into the receiving bore of the spindle and is fastened therein with expanding levers. The expanding levers may be positioned in their holding position via a pull rod and a pull bolt. For guiding the pull bolt and the pull rod the spindle further comprises a guide bushing. Due to the plurality of parts the clamping device requires a great constructive expenditure. The axial insertion step makes the changing of the tool holder more difficult and results in longer exchange times.
Another clamping device is known from German Offenlegungschrift 40 24 645 in which a cylindrical fitting lug of the tool holder extending into the cylindrical receiving bore of the spindle is provided with a transverse bore in which a clamping bolt is slidably arranged transverse to the axis of the fitting lug. A first conically shaped end extends into a conically shaped depression of a fastening screw, while the other end is provided with a conical depression into which the conically shaped tip of a further fastening screw extends. The axes of the two diagonally opposed fastening screws are aligned relative to one another and are spaced relative to the axis of the clamping bolt. When one of the two fastening screws is turned inwardly, the axial clamping between the tool holder and the spindle is achieved by the conical surfaces of the fastening screw and the clamping bolt contacting one another. The axial staggering between the clamping bolt and the fastening screws requires an exact manufacturing of the fitting lug of the tool holder as well as the positioning of the bores for receiving the fastening screws so that the manufacture of the clamping device is very expensive. Furthermore, due to the insertion step the exchange time is again relatively long.
It is therefore an object of the present invention to provide a clamping device of the aforementioned kind which is comprised of only a few parts, which is easy and inexpensive to manufacture, and which is embodied such that the tool holder, respectively, the tool may be exchanged within a short period of time.